Scam posed as Apple pop up which says my computer is infected? It's stopped my browser and won't let go. It's called macsecurity.com and wants me to call 844-743-8738.

How do I get rid of a popup which says my computer is infected? It's stopped my browser and won't let go. It's called macsecurity.com and wants me to call 844-743-8738. Sadly, I called the pop up. They ask what type of Mac you are using and then tell you how to unfreeze your computer. Then they have you log onto this website called www.fastsupport.com and they tell you how to log onto the secure browser "in order to stop the hackers from continuing to hack my computer". Then they take full contril of your screen and start showing you these codes that are the hackers (when I'm reality the hacker is the man on the phone). They then tell you that as a partner of Apple in order to get full protection you must pay a fee. Now that's when I finally caught on that I was on the phone with the person hacking my computer. While in shock I hang up the phone and just hold onto the power button until my screen went blank. I truly felt like an idiot because I was just watching this show called Mr.Robot which is all about hackers. Anyway, I refuse to turn on my laptop out of paranoia. What should I do? If I turn on my computer will they still be sharing my screen?